Peruvian Amazon will get wetter and experience more severe floods, threatening wildlife

A growing body of evidence shows that climate change is having a direct hydrological impact on the Amazon.

A new study expands on these findings by examining climate change’s direct hydrological impact at the subregional scale, specifically in the Western Amazon.

The increased flood pulse in the Peruvian Amazon basin could impact riverine and floodplain species like the taricaya turtle.

The impacts of climate change on the Amazon basin is a subject of much scrutiny due to the region’s rich biodiversity and the important role of rainforests in maintaining a stable global climate.

A growing body of evidence shows that rising global temperatures are having a direct hydrological impact on the Amazon, leading to more prolonged and severe droughts in some areas while causing increased precipitation and floods in others.

One 2013 study, for instance, found that the Amazon River’s hydrological cycle has become more extreme over the past two decades, with a far wetter wet season across much of the basin even as the southern Amazon rainforest experienced severe droughts in 2005 and again in 2010.

A study released last year predicted that those will probably not be the last droughts to hit the Amazon in the near future. Researchers found that climate models project great increases in the frequency and area of drought in the Amazon in coming decades.

But increased droughts aren’t the only likely impact of rising global temperatures, as the models also projected increases in extreme precipitation. To put it simply, the rainy season will get wetter and the dry season will get drier throughout much of the Amazon.

Now a new study expands on these findings by examining climate change’s direct hydrological impact at the subregional scale, specifically in the Western Amazon.

Baby taricaya turtle. Photo by Claudia Véliz-Rosas.

In a paper published last month in the journal Environmental Research Letters, researchers predict a more pronounced increase in seasonal precipitation and rainfall fluctuations than drought and dry conditions in the Peruvian Amazon basin, effecting important tributaries to the Amazon River like the Marañon, Huallaga and Ulcayali rivers.

Zed Zulkafli, a researcher at Imperial College London and Universiti Putra Malaysia who was lead author of the paper, told Mongabay she and her colleagues found that climate models based on the Representative Concentration Pathway (RCP) scenarios in the UN Intergovernmental Panel on Climate Change’s Fifth Assessment Report project the wet season flood pulse in the Peruvian Amazon becoming far more extreme by the end of the 21st century.

RCP 4.5 is a so-called “stabilization scenario” in which our global climate begins to stabilize shortly after 2100. Zulkafli and team found that with that level of global warming, the 100 year flood levels in the Peruvian Amazon basin would increase 7.5 percent. That increases to 12 percent under RCP 8.5, which is a scenario in which we essentially carry on with business as usual and greenhouse gas emissions levels continue to rise.

“This could impact riverine and floodplain species,” Zulkafli said. “The taricaya turtle, for example, rely on the sand banks formed after the river flooding as their breeding grounds.”

In the paper, Zulkafli and colleagues write that their findings are especially important to highlight as droughts seem to get most of the attention.

The increased flood pulse in the Peruvian Amazon will not only impact the reproductive processes of in-stream species but also the socio-economic stability of the communities that live on the floodplain, yet these impacts are less well known “amidst a growing literature that more strongly emphasizes future droughts and their impact on the viability of the rainforest system over greater Amazonia.”

The researchers note that it’s just as important to study the impacts of climate change on tropical forests and rivers at the sub-regional level as it is to understand the broader context, which includes not only forest-wide impacts but also land use change and other man made drivers of deforestation and forest degradation, such as the building of hydroelectric dams.

“Given the potential ecological and socio-economic impacts,” Zulkafli and her co-authors write, “a better understanding [of] the interplay between these different drivers on the hydrology of this region is highly timely.”

The taricaya turtle relies on the sand banks formed after the river flooding as breeding grounds. Photo by Claudia Véliz-Rosas.